Method for converting heavier oils into lighter oils



Dec. 3, 1929. R. J. BLACK 1,737,634

METHOD FOR CONVERTING HEAVIER OILS INTO LIGHTER 'OILS Filed Aug. 3, 1923 2 Sheets-Sheet 1 01/ Pump jg INVENTO R ATTORNEYS Dec. 3, 1929. R. J. BLACK 1,737,534

METHOD FOR CONVERTING HEAVIER OILS INTO LIGHTER OILS Filed Aug. 5, 1925 2 Sheets-Sheet 2 ATTORNEY Patented Dec. 3, 1929 UNITEDSTATES PATENT OFFICE" ROBERT J. BLACK, or HAMMOND, INDIANA, ASSIGNOR T sIIIcLAIR REFINING corr- PANY, OE cIIIcAeo, ILLINOIS, A. CORPORATION or MAINE METHOD FOR CONVERTING HEAVIER OILS INTO LIGHTER OILS Application filed August 3,1923. Serial No. 655,448. i

This invention relates to an improved method for the cqnversion of high boiling petroleum hydrocarbons hydrocarbons.

In the so-called cracking or destructive distillation of heavier fractions of crude petroleum by distillation under pressure, the heavier ydrocarbons are broken down and converted tota greater or less extent intolower boiling hydrocarbons. Attempts have been made to operate pressure stills in such a manner that only commercially valuable products will be given 011', but with existing methods, certain waste p'roductsare always given off during a pressure still run, particularly carbon or coke and non-condensible gases.

Attempts have been made to utilize'the non-condensible gases given off by a pressure still, as, for example, by burning them as fuel, but only the fuel value of the gases is utilized in this way. The non-condensible gases, usually amounting to around 2 to 10%, are commonly treated as a refining loss. 1

According to the present invention, these permanent gases are utilized in a particular-'- ly advantageous way withmaterial reduction in therefining loss and with increase in the amount ofgasoline produced, thus making the pressure distillation a more profitable methodof operation.

According to the present invention, substantially Y all of the so-called' permanent gases given off during the operation of the pressure still are absorbed by and admixed with the feed oil charged into the pressure into lower boiling.

Instead of absorbing. the non-condensibleoit containing the gases absorbed and entrained therein into the pressure still,

gases contain not only non-condensible gases but also .condensible and liquefiable constituents and. attempts have been made to recover these constituents by absorbing them in a hydrocarbon oil from which the condensible constituents are recovered by redistillation, the absorbent oil being then utilized again for the absorption of further amounts of con- It is Well known that certain hydrocarbon I densible'constituents. In such scrubbing or condensing operations the permanent gas passes ofl' practically unabsorbed. According to the present invention, hydrocarbon gases containing such liquefiable constituents, may be absorbed in and admixedwith the feed oil along with the non-condensible gases; and the process of the present invention provides an advantageous method of recovering such condensible constituents without) the necessity of utilizing a separate absorption and distillation process.

The invention is of particular application in pressure distillation processes which are operated continuously or with continuous introduction of fresh feed oil during the progress of the cracking operation. In such continuous processes, the permanent gases given off during the pressure distillation may, to a greater or less extent, be absorbedin the feedv oil and returned therewith to the pressure still. Suchcondensible constituents of the gases as have escaped condensation in the .condenser can advantageously-be recovered by returning them to the still along with the feed oil. I

- Absorption of the gases in thefeed oil can be carried out in a substantially continuous 'mannerby forcing the 'gasesunder pressure into the feed oil, for example, by passing the oil and gases under pressure into or through an absorber where the are brought into intimate contact and w ere the pressure will serve to promote absorption and saturation ofthe oil with the gas.

The entire amount of non-condensible gas from the pressure still may in some cases be absorbed in the feed oil, ora part only of the gases may be so absorbed. It will be evident "the feed oil or separately, in which case the advantages incident to the return of the unabsorbed gases will be obtained in addition to those resulting from the return of the gases absorbed or dissolved in the feed oil.

The feed oil containing the gases absorbed and entrained therein under pressure can be introduced directly into the body of oil in the still or into a reflux tower; and, in the case of a circulating body of oil, they may be introduced into the circulatory stream. One advantageous method of operation is to introduce the feed oil directly into the bottom of the body of hot oil in the pressure still so that both the feed oil and the gases absorbed therein, either withor without additional unabsorbed gases, will be subjected to the high temperature prevailing in the oil into which the feed is introduced. The heating of the feed oil by bringing it into the body of oil heated to the cracking temperature will tend to drive out of solution part or all of the gases absorbed in the feed oil while cold, but this setting free of the gases will assist in distributing the feed oil in the body of the hot oil, and the gases driven out of solution will be brought into intimate contact with the hot body of oil at substantially the point of maximum temperature in the pressure still, so that opportunity for reaction between the gases and the hot oil Will be presented. The setting free of the gases from their solution in the feed oil will also serve to agitate. the body of oil, and the gases escaping from the body of oil into the vapor space of the still will have afurther opportunity of reacting therein.

In the operation of a pressure still, when permanent gas is removed during the distillation, further amounts of permanent gas form, and an equilibrium appears to be continually re-established. By re-introducing substantially all of the gases into the still, the

I formation of further amounts of permanent gas is prevented or retarded, while the gas which is returned appears to combine to a yery considerable extent, with the resulting improvement in the amount of gasoline produced as well as in its quality, and the permanent gases which are withdrawn will tend to" become more saturated, while the tendency to form coke is also retarded.

The manner in which the gases are absorbed in the feed oil, can be varied, as well as the amount of the gases and condens'ible vapors so absorbed. Where the gases are obtained from some other source than the pressure still itself, for example, where the gases are those given off by a coke still, the gases may be compressed by a'suitable pump and forced into the feed oil. undera pressure somewhat greater than that maintained in the pressure still. Where the gases are those given off by the pressure still itself, these gases, if collected in a low pressure receiver or gas holder, may similarly be compressed and forced into the feed oil under a pressure somewhat in excess of that in the pressure still.

The invention will be further described in connection with the accompanying drawings illustrating certain preferred embodiments of apparatus adapted for carrying out the process of the invention, but it will be understood that the invention is illustrated by these embodiments and is not limited thereto.

In the accompanying drawings, Fig. 1 shows, in a somewhat schematic and diagrammatic manner, partly in plan and partly in elevation, one arrangement of the apparatus, and Fig. 2 shows, in a similarly schematic and diagrammatic manner, partly in plan and partly in elevation, anotherarrangement of the apparatus.

Referring first to the apparatus shown in Fig. 1, a pressure still of the shell type is indicated by 1, having a reflux tower 2 thereon, from which the vapors and uncondensed gases escape through the line 3 to the condensing coil 4, the pressure being either reduced by a suitable pressure regulating valve 4 between the still and the condenser or being controlled by a pressure-reducing valve arranged beyond the condenser. The condensed liquid escapes from the condenser 4 to the receiver 5, while the permanent gas passes to the gas receiver 6, which may have a gas line 6 leading to a gasometer or a suitable place of gas storage or use. receiver the gas is pumped to the gas absorption tank 7. V A

The feed oil, such as gas oil charging stock, is supplied from the tank 8, by means of the oil pump 9 through the line 10 to the gas absorption tank, where the cold feed oilis brought into intimate contact with the high pressure gases. With cold feed stock and with gases introduced at a high pressure, a rapid absorption of a considerable amount of gas takes place, which absorption can be promoted by suitable means for bringing the oil and gas into more intimate contact, for example, by introducing the gas and oil beneath a-perforated plate or through injector nozzles and thereby increasing the intimacy From the gas of contact of the gas and oil. From the gas absorption tank 7 the oil with absorbed as,

and either with or without excess unabsor ed gases out of solution, more or less rapidly.

This escape of gas from the cooler feed oil into the hotter body of oil in the pressure still will promote inter-mixture and agitation of the oil, while the gases themselves will be brought into intimate contact both with the hot liquid oil and with'the hot vapors in the pressure still. The gases are thus introduced in a particularly advantageous manner into the heated body of oil and vapors where active cracking is taking place, and opportunity for reaction or re-combination of the gases with the oil and with the vapors'is thus provided. ,Such amounts of the gases as remain dissolved or absorbed in the feed oil will likewise be brought into intimate and reactive relation with the hot oil in the still as the cooler feed oil is intimately mixed therewith, thus providing added opportunity for reaction of the dissolved gases with other constituents in the pressure still. The introduction of the feed and absorbed admixed gases into the hottest portion of the still accordingly provides a most intimate contact of the gases with the unsaturated and reactive constituents in the still. 7

In the appara'tusillustrated diagrammatically in Fig. 1, if the pressure is released by means of a valve 4* between the still and the condenser, the gas in the gas receiver 6 will beat approximately .atmospheric pressure, and the pump willcompress this gas and force it into the gas absorption tank 7. Control over this gas absorption and injection is provided by placing valves between the low pressure gas receiving tank 6 and the compressor, and alsov between the compressor and the gas absorption tank 7; also by providing a by-pass (not shown) from the com-' pressor discharge to the low pressure gas receiving tank, which will permit excess gas to be circulated so that any desired degree of control isprovided. Where a part only of the gas is to be absorbed in the feed, the excess gas may escape through the pipe 6 to a gas receiver or storage tank.

Where all of the gases are not absorbed in the cold feed oil, the excess unabsorbed gas may also be forced into the gas absorption tank and carried 1 along with the feed oil to the pressure still. In this case, the amount of the gases introduced into the still will be greater than that which would be introduced in solution in the feed oil, and such unabsorbed gases will tend -to escape more rapidly through the body of hot oil into the vapor space of the pressure still, although a more or less intimate inter-mixture of the oil and unabsorbed gas may take place'in the feed line. Such excess gas will further tend to agitate the oil in the still and to promote the dissemination of the fresh feed throughout the body of hot oil in the still.

In the apparatus illustrated in Fig. 2. I I

have shown an arrangement adapted for the practice of the invention in connection with a pressure still such as that illustrated in U. S. Letters Patent No. 1,285,200 granted to the Sinclair Refining Company, November .19, 1918 on the application of Edward W.

Isom. In the apparatus thus illustrated, the

bulk supply tank 16 containing the main I body of oil is located away from the furnace and the oil is circulated from this bulk supply tank through the line 17 to the pump 18 and thence through the line 19 to the battery of tubes 20 suitably arranged in the heating flue of the furnace 21. From the upper end of the tubes 20 a line 22 leads back to the bulk supply tank. A reflux tower 23 is arrangedabove the bulk supply tank 16, being connected therewith by the vapor line 24 and the return oil line 25. The overhead distillate escapes through the pipe 26 to the condenser 27 leading to the receiver 28 for the pressure distillate. The uncondensed gas is collected in the gas receiver 29 and is pumped by the pump 30 to the absorber 31 to which the feed oil. is supplied from a suitable supply tank through the line 32. x v The feed oil with the gas absorbed therein under pressure, and either with or without excess unabsorbed gases, may be supplied either through the line 33, to the top of the reflux tower, and into the reflux tower at 34, or it can be supplied through the line 35, to the bearings 36 of the pump 18, where it may enter the circulatory stream of oil through the pump bearings. A line for drawing off tar and for initially charging the still is indicated at 37.

In the pressure'still illustrated in Fig. 2 the feed'oil containing the absorbed gases,

.and either with or without excess unabsorbed gas, may be introduced either into the reflux tower, or into the circulating oil through the pump hearings, or in part through each of these places. Where the feed is introduced into the top of the reflux tower it will be heated by coming in contact with the hot gases in the tower, and the absorbed gases will be more or less completely driven out culating line through the pump bearings, the pump Will serve to intermix the feed oil and hot circulating oil and will thus bring the feed 011 and gases into intimate contact with the hot oil; the resulting mixture will then be forced through the heating tubes where further opportunity will be provided for reactlon of the gases with the hot oil, while the gases will also promote the circulation of the oil through the vertical tubes by their air-lift action.

It is well known that a considerable portlon of unsaturated hydrocarbons are present both in the permanent gases and in the pressuredistillate from pressure stills, as well as 1n the olland vapor in the still itself during the cracklng operation. While I do not desire to limit myself by any theoretical explanatlon of the action which takes place when the permanent gases are returned to the stlll, according to the present invention, yet I believe that reaction takes place between the returned gases, to a greater or less extent, and the hot oil and oil vapors in the pressure still, and particularly between unsaturated constituents of the gases and the 0118 and vapors, and that this action is promoted by the intimate manner in which the gases are introduced in solution in the feed 011, and particularly Where the feed oil and absorbed and entrained gases are introduced lnto the hottest portion of the still where active reaction is presumably taking place.

The present invention results in an improvement in the quality and an increase in the amount of the gasoline distillate produced, giving a gasoline of a higher degree of saturation which is light in color and eas1er to refine than ordinary pressure dis tillate, thus reducing the refining loss, while increasing the amount of the gasoline distillate and facilitating the pressure still operatlon and control, as well as reducing the amount of permanent gases to be otherwise disposed of, and reducing the tendencyv toward coke formation. WVhile I have described and illustrated the invention as applied in the operation of two types of pressure stills, with which it may advantageously be practised, yet it will be understood that the invention is of more or less general application and can be practised in connection with pressure stills of various kinds, both tubular and of the shell type,

where more or less continuous feed of fresh oil takes place during the pressure still operation. Where the feed oil with absorbed and entrained gas is introduced into a circulatory system, such as a tubular cracking .coil, or system, the gases may assist the circulation while they will be brought into intimate contact with the hot oil while it is being circulated. I

It will be evident that the pressure and temperature maintained in the pressure still can be varied, and that the nature and amount of the charging stock to be fed to the pressure still may also be varied. In pressure stills of the kind illustrated, pressures of around 90 to 125 lbs. (for example) may be used, and the charging stock may be ordinary gas oil such as is used in pressure stills operated at such pressures.- Such gas 011 will,. when cold, rapidly absorb a large amount of the gases and will hold them in a dissolved or absorbed state, until the oil becomes heated upon introducing it into the pressure still. With tubular cracking stllls a lighter charging stock can be used, for example, a light gas oil or kerosene charging stock, and the gases may be smnlarlyabsorbedin it and introduced therewith into the tubular cracking still. In such a still the pressure may similarly be varied and pressures of, for example, 90 to 125 lbs. employed or much higher pressures, for example, around 600'01 700 lbs. employed.

It will thus be seen that the present 1nvention is of more or less general application for the utilization of hydrocarbon gases, either with or without admixture with liquefiable vapors, from pressure stills or other sources and enables such gases, or gases and vapors, to be utilized in a particularly advantageous manner. Where condensible vapors are present admixed with the gases, these vapors will be set free in the pressure still and Wlll be recovered with the pressure distillate, although further reaction may take place between them or certain of their constltuents such'as unsaturated constituents, and other liquid or vapor constituents present in the pressure still. The present invention accordingly provides an improved method of absorption and recovery of such condens ble vapors, while at the same time introducing permanent gases into the pressure still along with the charging oil therefor.

I claim:

1. The method of cracking heavier hydro-- 'carbonsto form lighter hydrocarbons which comprises subjecting a body of the heavier hydrocarbons to a craclnng temperature un der pressure, separating permanent gases from condensible Vapors resulting from the cracking operation and collecting the hydrocarbon gases at a lower pressure, recompressing such gases and forcing the gases under pressure into relatively cool hydrocarbon il and introducing the resulting oil, containing the absorbed and entrained gases, into the said body of oil maintained at a cracking temperature.

2. The method of cracking heavier hydrocarbons to form lighter hydrocarbons which comprises subjecting a body of'the heavier hydrocarbons to a cracking temperature under pressure, separating permanent gases from condensible vapors resulting from the cracking operation by condensing the latter and collecting the hydrocarbon gases at a lower pressure, recompressing such gases and forcing substantially all of them under pressure into relatively cool hydrocarbon oil and introducing the resulting oil, containing the absorbed and entrained gases into the said body of oil maintained at a cracking temperature.

3. The method of cracking heavier hydrocarbons to form lighter hydrocarbons which comprises subjecting a body of the heavier hydrocarbonsto a cracking temperature under pressure, condensing the resulting vapors and separating the permanent gases therefrom at a lower pressure, compressing the separated gases and injecting gases containing constituents separated from the cracked vapors into cool oil underpressure and introducing the cool oil with absorbed constituents contained therein directly into the body of oil maintained at the cracking temperature.

4:. The method of cracking heavier hydrocarbons to form lighterhydrocarbons which comprises subjecting a body of heavier hydrocarbons to a cracking temperature under pressure, withdrawing permanent gases and vapors generated and separating permanent gases from the readily condensible constituents at a lower-pressure, compressing gases containing constituents separated from the cracked vapors and injecting the gases so compressed into a body of relatively cool hydrocarbon oil under pressure, introducing oil from the last named body together with gaseous constituents'absorbed therein and admixed therewith directl into the body of oil maintained at the crac ing temperature. 5. The method of cracking heavier hydrocarbons to form lighter hydrocarbons which comprises subjecting a body of the heavier hydrocarbons to a cracking temperature under pressure, withdrawing permanent gases and vapors generated andseparating gases r from readily condensible constituents of the gas and-Vapor mixture at a lower pressure, compressin gases containing constituents separated rom the cracked vapors and inj ecting the gases so compressed into a body of relatively cool hydrocarbon oil maintained under pressureat least as high as the pressure maintained on the body of oil at the cracking temperature, introducing oil from the last named body together with gaseous constituents introduced thereinto directly into the body of oil maintained at the cracking temperature.

In testimony whereof I aflix m signature.

ROBERT J. LACK. 

